I am not really getting deep into the technology tree as it is mainly up to you. Paths through the tree are numerous. Remember not to get too ahead of yourself and cut a line for there is a lot of important things at the begining, but if your tech path leads you diffrent then what is below just do what ya can when ya can.
Alright, there are a few things you need to consider when you begin the game Size of the map, difficulty of the computer (including aggressive or not), type of civilization you are playing, and the force of the barbarians.
If you are playing Duel sized their isn't much space, you need to hurry a bit at the begining, and get your city down as fast as possible. With a small map or raging barbaians you still want to hurry, but 1-2 turns is usually a safe amount of turns to drop your city. (Note:1 means that turn). If the size of the map is larger, and if the barbarians are just on, you are usaly safe taking 2-4 turns. It is important though to take into consideration if you do though, that you are a few turns behind in the begining. Unless it was for a semi-diffrent change that you can use to quickly imporove your situation, you may have a harder time getting the begining wonders. Remember you can use two out, as your capital's culture is going to expand quickly, and try to get what bonuses you can in your first city, but remember to keep some kind of tree's,hills, or some kind of hammer producing tile inside your border, or that will slow you down as well. If.. If this happends where you get some good food, but really poor production then later remember to focus on workers or settlers, but I am getting ahead of myself.
Wherever it maybe after you drop your first city, start on a building. I perfer a barracks this early to get ready for the military units I am going to produce later from this city, but if you have another option that you perfer that will work as well. The goal is to get around 3 population. If your building finishes before this happends (which is usually true) start working on a fighter, and continue to just try to gain population points. If you have a worker (starting at later ages) now would be a good time to start working on food, and if you have an explorer/military unit.. This is the time to start looking around.
I should note for 'speed' sometimes people build a worker at 2 population... There is nothing wrong with this, but wether it is really faster is up to the techs you have, and the amount of food/production you have. If you have a few bonus tiles around you, and you are researching towards using those bonuses building one at 2 might actually be better for you. Beware flood planes, they may seem good, but especially at harder difficulties when you only get +1 health these can just kill your city growth.. so build around at your own risk. (Usually better for a second city)
When at 3 population it is time to start looking for where you are going to build your second city. If you found a good place, but the AI is near you then this is the time to build a settler, and try to rush them out there. But unless you must build a settler to take up a spot, it is usually better to try to put out a worker first. Hopefully by this time you have researched either the wheel, agiculture, mining, animal husbandry, and/or masonry (or something on the lines of being able to work the tiles around you).
If you aren't crowded (assume you are crowded on a duel map) then it is up to you wether you want to build another warrior first before your settler, or just to switch to your settler then. If you don't have your worker out imporving the land this can take a minute, but this process can be cut down by working the area around you (one of the bonuses of putting a worker out at 2 makes this faster if you had that worker workin'). When your improving the land look for what gives you the most. Corn is usually good, because it gives you a high number of food, and what is important is the total number of Production + food per that tile with a settler (this is also true for workers obviously). You don't /need/ to work every tile of the capital yet, and sometimes it is better to make a road to where you want to place the second city at this time so it is faster to get it there. Although this is safer if ya built that warrior after your barracks, usually this early you should be safe from everything but animals, and barbarians you happen to walk into.. *Be Carefull*
When your settler is done, before ya head him out you need a fighter to go with him. If you had already built one after the barracks you should be alright, but take the one you are 'going' to build right after him and take him instead. Your city will be empty, but at 3 population you will still be safe from unhappiness of not having a military unit. If ya take the one ya already built, just fortify the military unit you make after your settler there.
In your capital you have a choice now.. Continue expanding, go for a wonder, build more units, or even build some buildings you have researched. I would suggest another worker to get your cities developed faster, but if you want to get a begining wonder this is a good time to get started. If you do start on a building beware your cities unhappyness. If you are heading towards slavery, then some unhappy citizens might not be that bad, but those unhappy people aren't doing anything for you, and if not it might be a better idea just to stagnate at a point (if able) before you get one. This is also true if you start working on units, which if your city is now empty, or raging barbarians are on you should do immeditly.
If you want to expand by building another settler, beware of a few things. One, money.. you are going to have to pay more per turn for maintenance. Check the cost of the second city, and use that to 'guesstimate' how much more you will be paying. If you are fine with that, and still want to expand then go for it, but remember to have another military unit built before/after it to walk with him to his location. Note: You don't /have/ to have this unit, and you can still lose your settler with this one unit, but it is usually better to have him there with it unless rushed.
Alright, there are a few things you need to consider when you begin the game Size of the map, difficulty of the computer (including aggressive or not), type of civilization you are playing, and the force of the barbarians.
If you are playing Duel sized their isn't much space, you need to hurry a bit at the begining, and get your city down as fast as possible. With a small map or raging barbaians you still want to hurry, but 1-2 turns is usually a safe amount of turns to drop your city. (Note:1 means that turn). If the size of the map is larger, and if the barbarians are just on, you are usaly safe taking 2-4 turns. It is important though to take into consideration if you do though, that you are a few turns behind in the begining. Unless it was for a semi-diffrent change that you can use to quickly imporove your situation, you may have a harder time getting the begining wonders. Remember you can use two out, as your capital's culture is going to expand quickly, and try to get what bonuses you can in your first city, but remember to keep some kind of tree's,hills, or some kind of hammer producing tile inside your border, or that will slow you down as well. If.. If this happends where you get some good food, but really poor production then later remember to focus on workers or settlers, but I am getting ahead of myself.
Wherever it maybe after you drop your first city, start on a building. I perfer a barracks this early to get ready for the military units I am going to produce later from this city, but if you have another option that you perfer that will work as well. The goal is to get around 3 population. If your building finishes before this happends (which is usually true) start working on a fighter, and continue to just try to gain population points. If you have a worker (starting at later ages) now would be a good time to start working on food, and if you have an explorer/military unit.. This is the time to start looking around.
I should note for 'speed' sometimes people build a worker at 2 population... There is nothing wrong with this, but wether it is really faster is up to the techs you have, and the amount of food/production you have. If you have a few bonus tiles around you, and you are researching towards using those bonuses building one at 2 might actually be better for you. Beware flood planes, they may seem good, but especially at harder difficulties when you only get +1 health these can just kill your city growth.. so build around at your own risk. (Usually better for a second city)
When at 3 population it is time to start looking for where you are going to build your second city. If you found a good place, but the AI is near you then this is the time to build a settler, and try to rush them out there. But unless you must build a settler to take up a spot, it is usually better to try to put out a worker first. Hopefully by this time you have researched either the wheel, agiculture, mining, animal husbandry, and/or masonry (or something on the lines of being able to work the tiles around you).
If you aren't crowded (assume you are crowded on a duel map) then it is up to you wether you want to build another warrior first before your settler, or just to switch to your settler then. If you don't have your worker out imporving the land this can take a minute, but this process can be cut down by working the area around you (one of the bonuses of putting a worker out at 2 makes this faster if you had that worker workin'). When your improving the land look for what gives you the most. Corn is usually good, because it gives you a high number of food, and what is important is the total number of Production + food per that tile with a settler (this is also true for workers obviously). You don't /need/ to work every tile of the capital yet, and sometimes it is better to make a road to where you want to place the second city at this time so it is faster to get it there. Although this is safer if ya built that warrior after your barracks, usually this early you should be safe from everything but animals, and barbarians you happen to walk into.. *Be Carefull*
When your settler is done, before ya head him out you need a fighter to go with him. If you had already built one after the barracks you should be alright, but take the one you are 'going' to build right after him and take him instead. Your city will be empty, but at 3 population you will still be safe from unhappiness of not having a military unit. If ya take the one ya already built, just fortify the military unit you make after your settler there.
In your capital you have a choice now.. Continue expanding, go for a wonder, build more units, or even build some buildings you have researched. I would suggest another worker to get your cities developed faster, but if you want to get a begining wonder this is a good time to get started. If you do start on a building beware your cities unhappyness. If you are heading towards slavery, then some unhappy citizens might not be that bad, but those unhappy people aren't doing anything for you, and if not it might be a better idea just to stagnate at a point (if able) before you get one. This is also true if you start working on units, which if your city is now empty, or raging barbarians are on you should do immeditly.
If you want to expand by building another settler, beware of a few things. One, money.. you are going to have to pay more per turn for maintenance. Check the cost of the second city, and use that to 'guesstimate' how much more you will be paying. If you are fine with that, and still want to expand then go for it, but remember to have another military unit built before/after it to walk with him to his location. Note: You don't /have/ to have this unit, and you can still lose your settler with this one unit, but it is usually better to have him there with it unless rushed.